Producing lower alkyl esters



Patented Aug. 17, 1948 PRODUCING LOWER ALKYL ESTERS Robert Gardner King,Norwalk, and Robert JoshuaKing, New Canaan, Conn., assignors to ThePhoto 1echnical Corporation, Norwalk, Conn, a corporation of Connecticut7 No Drawing. gll p plication January 1, 1945,

7 Serial No. 571,016

[8 Claims. 01.260-4103) This invention relates to improvements in thepreparation of the lower alkyl esters of the fatty acids which occurnaturally in the form of glycerides.

A number of methods, of preparing the ,lower alkyl esters of the higherfatty acids from the naturally occurringfiglycerides. have been doscribed, including processes involving alcoholysis or re-esterification,carried out by heating, the glyceride with the lower alco hol, such asmethyl or ethyl alcohol in the presence of a catalyst, usually an alkalicatalyst although acid catalysts have been suggested and used undersubstantially anhydrous conditions. It has been generally consideredthat the reaction will not proceed in the presence of any substantialamount of water or in the presence of any substantial amount of freefatty acid in the fat or oil. In the procedures heretofore used,therefore, it has been necessaryto use substantially anhydrous alcohol,and to use refined fats or oils, substantially free fromwaterand withalow free fatty acid content or, in the case of oilsor fats withrelatively high fatty acid .content,- to

take special precautionasuch as the conversion thereof to soap, prior tocarrying out the-alcoholysis reaction. With alkali catalysts, anhydrousconditions, and the substantial absence of free fatty acid, high yieldsof the lower alkyl esters of primary alcohols can be obtained, and

the glycerine can be substantially recovered in fairly concentratedform. However, the-process is industrially difiicult, as it'is difficultto maintain substantially anhydrous conditions, and it is expensive toso refine the oil as to reduceni free fatty acid content sufiicientlyor, if compensation is made for the presence of the free fatty acid bythe addition of a saponifying agent, difficulties are encountered insoperating the giycerine from the alkyl esters which are formed,possibly because of the emulsifying action of the soap. The esters ofsecondary alcohols, .e. g, isopropyl, are produced with evengreaterdifiicul-ty and with very poor yields. Yields. withacidcatalysts, by method heretofore proposed, are not good with both primaryand secondaryalcohols.

The lower alkyl esters have a number of industrial applications as such,and are. con-veniently used for the production of soap, bysaponiiication.

esters. The process proceeds efiiciently even thou h the oil or a con an a ub n a p portion of free fatty acid, and makes unnecessary removingthe free fatty acids or converting them to soap with consequentdifficulties in separatin the l be a s yc ri h @1 holysis orre-esteriflcation proceeds to substantial completion and the separationof the sl cerine io med f om the a k ste s rmed is rapid andsubstantially complete.

In accordance with th e en nve i n. the lowerallsyl este s o the t y aco th f .Or oils as they naturally occur are prepared by the alcoholysis'or e-es rifica ie O he lyceride. with a lower alcohol, advantageously inthe presence of a substantial quantity of water, with the use of an acidus all ul ur c a id. and an .acidwomDfi tible: emulsifying agent,advanta- The present invention provides an improved 7 geouslymaho anyacids. The reaction proceeds readily at relatively low temperatures, andordinarily is carried out at reflux temperatures and with thoroughagitation. When the reaction has proceeded to substantial completeness,the reaction mixture is subj pt l 1 t t i tion. A lowerlayer, whichcontains the glycerine, acid, water andex ess alcohol dil s par t andmay be treated for the recovery of the glycerine and the excess alcohol.The upper oily layer consists of the lower alkyl esters of the y a idConversions ran -ins a hi h a 93 per cent or' higher, are obtained. Freefatty acid in the fat or oil used is converted to the lower alkyl esterin the course of the reaction, so that the alkyl esters produced willcontain but a very small amount of free fatty acid, even though theoriginal fat or oilcpntains asubstantialproportion of free fatty acid,Most of the impurities present in the original fat or oil will separateintothe lower layer.

The glycerine, isv readily recovered by neutralizing the lower layerwith solid soda ash .or

other alkali, filtering 9f the inorganic salts formed and d stilling.the excess alcohol and -water-froin the filtrate. If necessary, theglycduced impractical, whether the use is of the esters as such or forthe production of soap. In such case, the esters may be distilled undera relatively high vacuum, advantageously with the use of steam. Theseesters, particularly the methly and ethyl esters, distill at lowertemperatures than the free fatty acids do, and the distillation does notinvolve the formation of pitch or tar to the extent that thedistillation of fatty acids does. At least a portion of the mahoganyacid or other agent, such as toluene sulfonic acid, remains in the esterlayer, and the esters may be rapidly and completely split through theaction of this agent by the addition of dilute acid and carrying out thehydrolysis under conditions such that the alcohol, as formed, isdistilled off.

The invention will be illustrated by the following specific examples,but it is not limited thereto.

Example I One thousand parts of tallow having an acid value of about 5are melted and added to a solution or mixture containing parts of water,67 parts of 95% sulfuric acid, 330 parts of cornmercial methyl alcoholand parts of mahogany acid. The mixture is heated to refluxingtemperature for 12 hours with agitation. The heat is then shut off andthe mixture allowed to remain quiescent until it separates into twoclean layers. The lower layer, containing the glycerine, water andmethyl alcohol, is separated from the oily layer, consisting of themethyl esters of the tallow fatty acid. Conversion to the methyl esterswas in one case 97% of theoretical. glycerine-containing layer may betreated to re cover the glycerin by any suitable procedure, such as bytreating the lower layer, after separation from the oily layer, withsoda ash until neutral,

filtering off the sodium sulfate, and distilling off the methyl alcoholand water. The crude glycerine so obtained may be further purified byvac uum distillation. The oily layer, consisting of the methyl esters ofthe tallow fatty acids, is

The

washed with water or an aqueous solution of salt to facilitate theseparation of the glycerine, and to remove such impurities as may beremoved by this washing. If, in this procedure, tallow fatty acids areused in place of tallow a high yield of the same methyl esters isobtained, but, of course, no glycerine is obtained as a byproduct.

Example II One thousand parts of tallow are melted and added to asolution or mixture containing 100 parts sulfuric acid, 650 parts of 91%isopropyl alcohol and 20 parts of mahogany acids. The mixture isrefluxed for 12 hours with agitation. The heat is then shut off and themixture al-. lowed to settle, whereupon it separates into a lower layerand a floating oily layer consisting of about 95% isopropyl esters ofthe tallow fatty acids, which latter layer may be washed with water oran aqueous salt solution to facilitate the settling and separation.

Advantageously, the quantity of water present in the reaction mixture inthe practice of the present invention is substantial, although anhydrousor substantially anhydrous conditions may be used. It may range as highas 50% of the total mixture of water and alcohol, or even higher, e. g.,up to 90% or somewhat more. Ordinarily, to reduce the reaction volume asmuch as is feasible, such large quantities of water as- 50% will not beused, but smaller quantities,

such as 10 to 20%, based on the alcohol, will be used. One of theadvantages of the presence of water in the reaction mixture is that itpermits the use of sulfuric acid as a catalytic agent without incurringrisk of side reactions, such as the formation of ethers, charring, orthe like, which results from the use of concentrated sulfuric acid.

Instead of sulfuric acid, other acids, such as hydrochloric acid orphosphoric acid, or acid salts, such as acid sodium sulfate, may beused, but because of its economy, sulfuric acid is the acid of choice.

One of the indications of the eficiency of the process of the presentinvention is that even secondary alcohol, such as the isopropyl alcoholof Example II, may be used in the re-esterification reaction with highefiiciency. Most of the processes heretofore proposed have not beenworkable with secondary alcohols, such as isopropyl alcohol, at least inthe sense that substantial conversion of the glyceride to the alkylester has not been obtainable. Any of the lower alcohols, includingmethyl, ethyl, iso and normal propyl, butyl and amyl alcohols may beused in the practice of the invention. Tertiary alcohols, such astertiary butyl alcohol, may also be used, as may mixtures of alcohols,to produce mixed esters.

While the use of the mahogany acids is of marked advantage, as comparedwith other acidcompatible emulsifying agents, in promoting theefficiency and completeness of the re-esterification reaction, otheragents such as toluene sulfonic acid, naphthalene or alkyl naphthalenesulfonic acids, etc., in general, the acid-compatible emulsifyingagents, promote the efficiency and completeness of the reaction.

The invention is applicable to the production of the lower alkyl estersof any of the naturally occurring fatty acids, and in particular, to there-esterification or alcoholysis of any of the natural fats or oils,including tallow, coconut oil, olive oil, palm oil, sardine oil, castoroil, whale oil, linseed oil, cocoa butter, etc. It may also be appliedto the esterification of the free acids with the alcohol or alcohols,similar conditions being used.

We claim:

1. The process of producing lower alkyl esters of higher fatty acidswhich comprises reacting a material of the class consisting of higherfatty acid glycerides and higher fatty acids with a lower alcohol in thepresence of a mineral acid, an acid-compatible emulsifying agent andwater.

2. The process of producing lower alkyl esters of higher fatty acidswhich comprises reacting a material of the class consisting of higherfatty acid glycerides and higher fatty acids with an aqueous loweralcohol in the presence of a mineral acid and a sulfonic acidemulsifying agent.

3. The process as in claim 1 in which the acid is sulfuric acid.

4. The process as in claim 1 in which the agent is mahogany acid.

5. The process as in claim 2 in which the acid is sulfuric acid.

6. The process as in claim 2 in which the agent is mahogany acid.

7. The process of producing lower alkyl esters if higher fatty acids byre-esterification or alcoholysis of higher fatty acid glycerides whichcomprises reacting a higher fatty acid glyceride with an aqueous loweralcohol in the presence of sulfuric acid and mahogany acids, thequantity of water in the reaction mixture being at least REFERENCESCITED based on the lower 1 The following references are of record in the8. The process of producing lower alkyl esters file of this patent:

of higher fatty acids which comprises reacting a material of the classconsisting of higher fatty 5 UNITED STATES PATENTS acid glycerides andhigher fatty acids with a Number Name 7 Date lower alcohol in thepresence of a mineral acid, 290 609 G088 July 21 1942 n acid-compatibleemulsifying agent and water, 2371284 Cook Man 1945 separating the esterlayer from the aqueous layer e Percy Aug 1945 and ysi g it whiledistilling ofi liber 10 alcohol.

ROBERT GARDNER KING. ROBERT JOSHUA. KING.

